Flue or vent



Sept. 13, 1932. I J. A. STADTFELD 1,876,733

' FLUE on VENT Filed Sept. 28, 19,29

INVENTOR .74605 A. arnormsza ms ATTORNEY PatentedS'e pt. 1932' j JACOB A. STADTFELD,

& ASBESTOS WORKS, OF SAN FRANCISCO, CALIFORNIA, A CORPORATION rormm -M invention relates tov pipes for carrying ofi t e products of combustion arising from appliances such as furnaces, heaters, ovens and 'smelters; andesp ecially to flues an '5 vents forcarrying off the roducts of combustion arising fromappliances employing carbonaceous or hydrocarbon fuel.

An object of the invention is the provision of a fine, of the character described which is light, durable, heat insulating and acid-resistant. v I

Another object of the invention isthe rovision of a flue which is of low heat con activity, so as to preclude cooling of gases passj ing therethrough and thereby permit such gases to pass readil through the flue.

. Another object of the invention is the provision of a flue which is of economical construction, and which can be conveniently and 2c readily manufactured.

* My 'invention'possesses other objects and valuable features, .some of which will be set forth in theifollowing description of my invention which is illustrated in the drawing forming part of the specification. It is to be understood that I do not limit myself to the showing made by the said description and drawing, as I may adopt varying forms 0 mykionvention within the scope of theclaims. '30 v ferring to the drawing: A The figure is an isometric view of a portion of the'flue of my invention; a portion of the structure is omitted from the view to show more clearly its construction.

Pi es for carryingofi products of combustion ave heretofore been made of such materials as galvanized iron, copper and terra cotta. ,Metal pipes, most commonl used, are veiy good heat conductors and irther- 40 more react-readily with dilute acid. Because of these properties they cannot be efiectively used as flues or vents, since water vapor which is usually present in the products of combustion, is quickly condensed on their inner walls. Moisture so condensed then reor sex FRANCISCO, cnrrormn, nssrenon 'ro PLANT RUBBER or canr'nun on ma.

' Application fled September 28, 19 89. Serial fie. 895,986.

acts with the sul hur content present .in the products of com ustion to form sulphurous acid; and the acid eats away the interior of the pipes. Not only is the life of the pipes decrea ed, but the pin holes first formed, by action of t e acid or corrosion, are'decidedly objectionab e inasmuch as they permit the poisonous gases carried by the pipes to es cape into the furnace rooms of. the buildings so equipped.

v An additional disadvantage of metal pipes is the fact that their high heat conductivity cools t e gases conveyed therein, so rapidly, that their rate of travel is materially diminished. This causes the cool gases to act as a stopper for the column of gases beneath them. This stopper efiect creates a back draft which forces the products of combustion through the above mentioned pin holes and through the air registers of the furnaces. F

Lead and Monel-metal pipes are pIOhlbltive because of their costs; and they do not prevent moisture condensation nor the consequent stopper action due to the too rapid cool- The objectionable physical pipes when used for therbfore twoing of the gases. characteristics of metal the purposes described are f fold,'their high heat conductivity and their non-resistance to the action of sulphurous and other acids. Because of these objections, some city ordinances now, require the installation oiterra cotta or cement flues and vents.

Terra cotta and cement tile flues are fairly good insulators when dry, but readily absorb moisture and thereby become fairly good conductors. On becoming saturated with moisture, there is a consequent formation of dilute sulphuric acid which, in the case of cement pipe, soon breaks down the flue. Once hav- 1n become good conductors, the same stopper e ect takes place within them as with the metal flues. Another objection to these flues is that since the various sections are joined b cement and since itis practically'impossible to use a cenientwhich has a coeflicient and basements of expansion equal to that of the flues, a tight joint ca'I'mot bemaintained. 'Furthermorethe weight of these pipes increases transportation cost; My invention is designed to obviate the above difli'culties, by the provision of a light, but yet heat-resistant, heat-insulating .and acid-resistant flue. In terms of broad inclu-. sion, the flue of my invention comprises a tube of fibrous material impregnated with a' heat-insulating and acid-resistant binder. Preferably, the tube is provided with a coating of a character similar to that-of the binder. In greater detail, the flue of 'my invention is ma e by impregnating a flexible sheet of suitable fibrous material, such as asbestos I paper or felting such as so-called roofing felt, with a cementitiousbinder which is rendered solid, moisture-proof, heat-insulating and acid-resistant upon baking. Asbestos paper is preferred due to the well known insulating andfire-resistant properties thereof. The impregnating composition or, cement employed, preferably comprises a homogeneous mixture of the following ingredients in substantially the proportions stated:

- Water glass (40% solution of sodium silicate in water) 12 lbs. (1 gal.)

Silica (preferably finely divided particles) 13 lbs. Zinc oxide (commercial) 2 lbs.

Lead sulphate (contained as impurity in 2 lbs. of commercial zinc oxide) .02 lbs.

Although the preceding proportions of ingredients have been found to give the best re- 40 sults, it has been found that the ingredients of the composition may be varied, with satisfactory results, within the following ranges Lead sulphate (,containedIasimpur ity in the commercial zinc oxide)- .01 to .1

If so desired between .1 to 1 lb. of lead carbonate may be also incorporated in the cement.

an alkali metal silicate may be employed, such as potassium silicate. For the silica, which ser'vesas a filler, equivalent quantities .of other fillers such as kieselguhr, diatoma: ceous earth, infusorial earth, fossil flour,

. round. glass, and/or powdered asbestos may e used. Also chemically equivalent quantities of metal compounds, such as calcium 5 oxide, manganese dioxide, lead. oxide and/or lead sul hate have been found satisfactory in place 0 the zinc oxide; and if so desired, C. P. zinc. oxide may be employed instead of the commercial oxide which contains lead sulphate as an impurity.

The fibrous sheet is subjected to the impregnating mixture in any suitable manner, and preferably until the sheet is thoroughly saturated, which may be facilitated by passing the sheet through any suitable squeeze 7 rollers, according to well known practice for impregnating fibrous sheet materiaL, After saturation, the sheet is then wound on a mandrel so as to form a laminated tube; the size of the mandrel being predetermined so in accordance with the size of the tube desired, and the width of the sheet being predetermined in accordance with desired number of laminations'. As illustrated in the drawing, I have found that for most purposes three laminations, 1, 2 and 3, will provide a sufli-' 'ciently rigid and efiicacious pipe. The tube,

thus formed, is slipped from the mandrel and is allowed to-air dry for sufficient time, so

as to enable handling of the tube without it bei mg distorted. From 20 to 24 hours of air drying is generally suflicient. When air dried, the tube is'baked; preferably -ina muflle furnace, at a temperature of between 210 to 300 F. forfrom 4% to 6 hours, or until the binder has become sufliciently solid and vitrified.

The baking process affects a chemical reaction between the alkali metal silicate and metal compounds inthe cementitious binder, to produce a water insoluble metal silicate in which is uniformly entrained the filler, thus providing a light, rigid, acid-resistant and heat-insulating binder.

In order to enhance the wearing qualities 1 5 of the pipe and insure its eflicacy it is provided with a coating 4:, of material similar to that of the binder. After the first baking process above described, the pipe is allowed to cool; and it is then dipped in or passed 1 through a mixture similarto that employed 9 in the impregnating process, but thinned down to dipping consistency with an aqueous solution of an alkali metal silicate such as sodium silicate. The coating is allowed to set sufliciently by air drying to enable handling of the pipe; and the pipe is then assed through or dipped in a bath; prefera l'y of Q calcium chloride and water, mixedin the pm- In place of the sodium silicate, equ1va-. lent quantities of other aqueous solutions of 1 portions to 1% lbs. of the salt to each gallon of water. After-this, the pipe is again baked at a temperature of between 175 F. and 225 F. for approximately four'hours; after which baking the pipe is allowed to cool, and is ready foruse.

The second baking effects a chemical reaction between the calcium chloride and excess of alkali metal silicate em loyed in the second treating mixture, and etweentheother =metal compounds insaid mixture and the alkali metal silicate, to form a coating which is similar in properties to that of the binder.

As a substitute for calcium chloride employed after the pipe is coated with the thinned bath of cementitious mixture, chemically equivalent quantities of other water s0luble salts such as magnesium chloride or calcium nitrate may be used.

The temperatures mentioned for baking, are those which have been found most satisfactory although the pipe may be baked at temperatures as high at 800 F., for relatively short periods. The latter is not generally desirable, however, as it might burn.

the fibrous material and destroy the strength of the pipe. As related above, after each treatment with the cementitious mixture, the pipe is allowed to air dry so as to permit handling thereof. This air drying generally takes approximately 24 hours. If it. is desired to save time, I have found that in place of air drying for the purposes described, the pipe may be dried at around 125 to 150 F. for about 1 to 1% hours.

For joining sections of pipe of my invention, a short sleeve, of the same construction as the pipes, is telescoped over abutting ends, and cemented thereto with a cement having substantially the same composition as the impregnating cement used in the manufacture of the pipes. For all practical purposes, such cement solidifies sufficiently on air drying to make a solid joint having a coefficient of ex pansion equal to that of the flue itself.

Pipes constructed in accordance with the teachings of my invention are good heat insulators; therefore, flues constructed therefrom convey away products of combustion without allowing them to cool sufficiently, so as to cause a condensation of their moisture content. As a direct result of this, as previously explained, the so-ealled stopper action or back draft caused by fiues made of good heat conductors is eliminated, or materially reduced.

Nhat little acid that is formed by the reaction between the sulphur content in the products of combustion and any water vapor which might possibly condense on the walls of the flue, can do no harm, since as previously explained, the pipes of my invention are acidresistant.

The pipes may be readily out to desired size by an ordinary cross out saw, and being materially lighter than either metal or terra cotta pipes, their cost of transportation is proportionately lower.

1 claim:

1. Asa new article of manufacture, a pipe for carrying off products of combustion comprising a tube of fibrous material hardened and compacted by a vitrified binder perme ating its fibres to provide a unitary rigid flue structure capable of self-support.

2. As a new article of manufacture, a pipe my hand.

, JACOB A. STADTFELD. 

